Method of preparing sound metal coatings



METHOD OF PREPARING SOUND METAL COATINGS Filed Nov. 24, 1964 INVENTOR. ARTHUR T. CAPE aim ATTOR N EYS United States Patent Oflice 3,262,804 Patented July 26, 1966 3,262,804 METHOD OF PREPARING SOUND METAL COATINGS Arthur T. Cape, Monterey, Calif., assignor to Coast Metals, Inc., Little Ferry, N.J., a corporation of Delaware Filed Nov. 24, 1964, Ser. No. 413,419 3 Claims. (Cl. 117-8) This application is a continuation-in-part of my copendin-g application Serial N 0. 114,626, filed June 5, 1961, now abandoned.

This invention relates generally to the preparation of sound metal surface coatings or deposits on metal parts or articles, such coatings or deposits being used as wear or protective surfaces for the parts or articles.

The method consists generally in pro-placing the alloy which is to form the coating or deposit, and assuring freedom from porosity in the coating or deposit, by coating the surface of such alloy prior to melting, with a layer of silica, which may be provided either in the vform of silica powder, or as a product derived, during the melting, from any organic chemical compound which decomposes under heat, to form silica, or which, when heated, reacts with oxygen to form silica. Among such compounds may be mentioned organic silicates, including ethyl silicate, as well as silicones, silanes, etc.

The term pre-placing, as used above, is intended to cover a number of methods of applying the alloy which is to form the coating or deposit, to the base metal or parts to which the coating or deposit is applied. This includes the following:

(1) Placing the alloy, in powder form, on the metal part or article, and maintaining the loose powder in place, as by means of a mold or similar retaining means for the powder. In this method, a layer of the silica powder is placed over the alloy. If ethyl silicate or other organic compound to which reference has been made is used, instead of silica powder, the ethyl silicate or other compound is sprayed or otherwise applied over the alloy.

(2) Applying the alloy by flame-spraying the alloy onto the metal part or article. In such case, the alloy sticks to the part or article, but does not usually melt into a homogeneous mass. The melting is done subsequently. In this method, the layer of silica powder or the ethyl silicate or other compound is applied over the flamesprayed alloy in any desired manner.

(3) Compressing and/or sintering the alloy, in powder form, into the desired form of the coating, applying it to the part or article, and subsequently melting the formed coating. In such cases, a binder is usually used to hold the powder particles together during compressing and/ or sintering. In this method, the layer of silica powder or the ethyl silicate or other compound is applied over the formed coating in any desired manner.

(4) Casting the alloy into a form which may be applied to the part or article to form the coating, the coating being subsequently melted. in this method, the layer of silica powder or the ethyl silicate or other compound is applied over the cast coating in any desired manner.

After the alloy has thus been pie-placed, the part or article is placed in a furnace containing an atmosphere, which may be hydrogen, mixtures of hydrogen with other gases such as carbon monoxide and nitrogen, argon, nitrogen alone, helium, etc., and the part or article is then heated in a manner to completely melt the alloy to thereby provide the desired coating or deposit on the part or article. In some cases, no special atmosphere is required in the furnace.

The temperature to which the part or article is heated will depend on the materials from which the base metals (part or article) is made, as well as on the nature of the alloy which is used as the coating.

Due to the presence of the silica powder or ethyl silicate or other compound used to provide the silica, the resulting melted coating is entirely free from porosity and other defects, and is entirely homogeneous in character. The silica, during melting of the coating, is not absorbed to any appreciable extent by the melted deposit, but, instead, forms a sinter or crust on the deposit, which falls off, or may be easily picked off. In this connection, it is to be noted that it is important that the silica not be contaminated with or mixed to any appreciable degree lWltll other materials which might interfere to any extent with the formation of the melted coating on the article, or which might be absorbed by or become alloyed with the melted coating. Among such undesirable materials may be mentioned aluminum oxide, alkali metal oxides, clay, sodium silicate, potassium silicate, feldspar, enamel frit, sodium carbonate, cobalt oxide, nickel oxide, zinciferous materials, and the like.

The method is applicable in the coating of a large variety of base metals, including plain and medium carbon steels, high temperature metals, etc. It is also applicable to a large variety of coating materials, such as hard facing and brazing compositions of all kinds, including nickel-base and cobalt base alloys, iron-base alloys, manganese-base alloys, etc.

The accompanying drawing illustrates a specific example of how the method or process is carried out.

In the drawing, a slab 1 of SAE 1045 steel, and of a thickness of about 1 inch, is provided at its periphery with a continuous wall or dam 2 of steel, which may be spot welded or otherwise secured to the slab to temporarily retain it in position during the coating of the slab.

The slab is uniformly covered, to a depth of about A", with a hard facing alloy 3, consisting, in this instance, of a cobalt-base alloy, in powder form, of the following composition:

Percent Boron 1.5 Silicon 3.0 Carbon 0.5 Nickel 15.75 Chromium 2.6.00 Tungsten 9.00 Cobalt Balance There is then spread uniformly over the alloy 6, a thin layer 4, about inch in thickness, of silica powder.

The slab, thus covered, is placed in a furnace and heated in the furnace to a temperature of about 2300" F. for about one hour. This causes the alloy coating 3 to melt and become bonded to the slab 1, and, at the same time, the layer 4 of silica powder becomes fused or sintered, but does not penetrate the coating 3. It remains on the coating *3 and can be easily picked or brushed from said surface, exposing the coating 3 which is free from porosity and other defects. The wall or dam 2 may then be removed from the coated slab.

It is to be understood that slight changes may be made in the method, as described, without departing from the spirit of the invention or the scope of the appended claims.

Having thus described my invention, I claim:

1. The method which comprises applying a metallic alloy to a metal article to be coated with such alloy, said alloy selected from the group consisting of nickel-base, cobalt-base, iron-base and manganese base alloys, applying over such alloy a layer consisting of a material selected from the group consisting of silica powder, organic chemical compounds which decompose under heat to form silica, and organic compounds which, when heated, react with oxygen to form silica,.thereafter heating the article to melt said alloy and said silica, the alloy becoming bonded to said article, and the silica remaining on the alloy coating, and then removing the silica.

2. The method which comprises applying a metallic alloy to a metal article to be coated with said alloy, said alloy selected from the group consisting of nickel base, cobalt-base, iron-base and manganese-base alloys, applying over such alloy a layer consisting of a compound selected from the group consisting of silica powder, organic silicates, silicones and silanes, thereafter heating the article to melt'said alloy and the product resulting from the heating of said compound, the alloy becoming bonded to said article, and the product resulting from the heating of said compound remaining on the alloy coating, and then removing the product resulting from the heating of said compound.

'3. The method which comprises applying to a steel base a coating of a hard facing cobalt-base alloy in powder fomn, spreading uniformly over said coating a thin layer consisting of silica powder, heating the steel hase, alloy and silica powder to cause the coating to melt and become bonded to said 'base, and the silica powder to become fused or sintered, and then removing the fused or sintered silica powder.

References Cited by the Examiner UNITED STATES PATENTS 8/ 1931 Vance. 4/1960 Rittmann 29--490 X 

1. THE METHOD WHICH COMPRISES APPLYING A METALLIC ALLOY TO A METAL ARTICLE TO BE COATED WITH SUCH ALLOY, SAID ALLOY SELECTED FROM THE GROUP CONSISTING OF NICKEL-BASE, COBALT-BASE, IRON-BASE AND MANGANESE-BASE ALLOYS, APPLYING OVER SUCH ALLOY A LAYER CONSISTING OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF SILICA POWDER, ORGANIC CHEMICAL COMPOUNDS WHICH DECOMPOSE UNDER HEAT TO FORM SILICA, AND ORGANIC COMPOUNDS WHICH, WHEN HEATED, REACT WITH OXYGEN TO FORM SILICA, THEREAFTER HEATING THE ARTICLE TO MELT SAID ALLOY AND SAID SILICA, THE ALLOY BECOMING BONDED TO SAID ARTICLE, AND THE SILICA REMAINING ON THE ALLOY COATING, AND THEN REMOVING THE SILICA. 